Timeline for Can R values be averaged?
Current License: CC BY-SA 4.0
15 events
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| Dec 17, 2023 at 21:59 | vote | accept | David Levner | ||
| Dec 17, 2023 at 3:35 | comment | added | Amazon Dies In Darkness | I wish I did! I was hoping to learn from you! | |
| Dec 16, 2023 at 22:29 | comment | added | popham | @End Anti-Semitic Hate, I guess the "why" is because the steady state heat transfer rate isn't linear with R value, where linearity with U value and area makes the weighted average work for U values. I can't demonstrate it with a small paragraph. Just asserting it makes me feel like I'm "baffling with BS." If you have a small paragraph argument, I would love to hear it. | |
| Dec 16, 2023 at 22:29 | comment | added | SteveSh | But it is the weighted average of the U values, not the weighted average of the R values. This phenomenon happens quite frequently when reciprocals are involved. Here's a typical example. Say you're on a 20 mile trip, and travel the first 10 miles at 30 mph, and the second 10 miles at 10 mph. What's your average speed? No, it's not 20 mph, but rather 15 mph. | |
| Dec 16, 2023 at 21:57 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 21:50 | comment | added | Amazon Dies In Darkness | Great answer. Can you add a small paragraph about why it's not simply the weighted average? | |
| Dec 16, 2023 at 21:41 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 21:34 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 21:19 | comment | added | popham | @SteveSh, yeah, but I think this best answers the OP. I'll add a note to the end, though. The other answer touched on it, but it's worth having tidier notation under this answer. | |
| Dec 16, 2023 at 21:11 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 20:38 | comment | added | SteveSh | But I think it does work, averaging that is, if you use U-values instead of R-values. | |
| Dec 16, 2023 at 20:29 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 20:20 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 20:06 | history | edited | popham | CC BY-SA 4.0 |
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| Dec 16, 2023 at 19:50 | history | answered | popham | CC BY-SA 4.0 |